1. Field of the Invention
The present invention relates to an optical unit incorporating an optical element such as a light-emitting diode or phototransistor. The present invention also relates to a photo-interrupter utilizing such an optical unit.
2. Description of the Related Art
FIGS. 11 and 12 of the accompanying drawings show two different types of conventional LED devices. The one shown in FIG. 11 incorporates a surface-emitting LED, while the other shown in FIG. 12 incorporates a non-surface-emitting LED.
Specifically, the device 1 shown in FIG. 11 includes a domed resin package 2 in which a light-emitting element 3 is incorporated. The element 3 is mounted on a first lead 4 in electrical conduction therewith. The element 3 is connected to a second lead 5 by a wire W. The first lead 4 has an upper end 4a in which a cuplike recess 6 is formed to accommodate the element 3. The wall surface of the recess 6 is reflective so that the light emitted from the element 3 is effectively directed upward. At the recess 6, a transparent protector 7 is provided. The protector 7 is formed by pouring gelatinized silicone into the recess 6 and then solidifying it. Even in a semi-fluid state, the applied silicone is properly retained at the upper end of the lead 4 due to the cuplike recess 6.
As in the above-described device 1, the other device 13 shown in FIG. 12 includes a first lead 15, a second lead 16, a light-emitting element 17 mounted on the first lead 15, and a wire W connecting the element 17 to the second lead 16. Numeral 18 refers to a resin package. In the device 13, light is emitted laterally from a side surface of the element 17, as indicated by an arrow. Thus, differing from the above device 1, the light-emitting element 17 of the device 13 is not put in a cuplike recess, but put on the flat end surface 15a of the lead 15 to allow the emitted light to travel undisturbed.
As in the above device 1, the element 17 of the device 13 is covered by a resin protector 23 made by applying gelatinized silicone resin. However, in the device 13, no special measures are taken for retention of the applied resin material. Thus, the applied material may spread unduly over the upper end surface 15a of the lead 15 and even dribble down the lead 15. If this happens, the resulting protector 23 is formed by an insufficient amount of resin material, thereby failing to enclose the element 17 properly.
The present invention has been proposed under the circumstances described above. It is, therefore, an object of the present invention to provide a simple, but effective countermeasure for the above problems.
According to a first aspect of the present invention, there is provide an optical unit which includes: an optical element; a lead including an end surface, the end surface being formed with a dent in which the optical element is placed; and a protector enclosing the optical element. The dent includes both a bottom surface supporting the optical element and a side surface connected to the bottom surface. The side surface is formed with an opening to avoid complete encircling of the optical element.
Preferably, the bottom surface of the dent may be greater in width than the end surface of the lead.
Preferably, the optical unit of the present invention may further include a resin package enclosing the protector.
Preferably, the bottom surface of the dent may be flat and have a rounded outline.
Preferably, the side surface of the dent may include two slant portions facing each other, wherein the slant portions are arranged to flare out as proceeding away from the bottom surface of the dent.
Preferably, the optical element may include a light-emitting surface which stands perpendicular to the bottom surface of the dent.
Preferably, the optical unit of the present invention may further include an additional lead electrically connected to the optical element.
According to a second aspect of the present invention, there is provided a photo-interrupter which includes: a casing; and an optical unit accommodated in the casing. The optical unit includes an optical element, a lead formed with a dent for placing the optical element in, and a protector enclosing the optical element. The dent is provided with a bottom surface supporting the optical element and with a side surface connected to the bottom surface. The side surface is arranged to avoid complete encircling of the optical element.
According to a third aspect of the present invention, there is provided a method of making an optical unit. The method includes the steps of: forming a first lead and a second lead from a conductive member having a uniform thickness; forming a dent in the first lead, the dent having a bottom surface and a side surface; placing an optical element on the bottom surface of the dent; connecting the optical element to the second lead by a wire; forming a transparent protector for covering the optical element; and forming a resin package for covering the first and the second leads, the wire and the protector. The side surface of the dent is arranged to avoid complete encircling of the optical element.
Preferably, the dent may be formed by subjecting the first lead to coining.
Other features and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings.